This invention relates to a breakout prediction system in a continuous casting process.
In the continuous casting process, molten iron reserved in a casting ladle is poured through a tundish into a mold, as well known in the art. The molten iron in the mold is gradually cooled and solidified to be drawn out from a lower portion of the mold as a strand. When the molten iron is cooled within the mold, a solidified portion called a shell is formed on a surface of the molten iron that is in contact with an internal wall of the mold. The continuous casting process suffers from a serious problem that the shell in the mold is often cracked or broken due to various factors. When a cracked portion of the shell reaches a bottom of the mold, the molten iron in the shell leaks out from the mold. Such an accident is called "breakout". Occurrence of the breakout results in interruption of the continuous casting process and must be avoided. In order to avoid occurrence of the breakout, it is required to detect presence of the cracked portion in the shell. Upon detection of the presence, the cracked portion is solidified again by decreasing an operation speed in drawing the strand.
When the shell is cracked in the mold, the mold and the molten iron are brought into direct contact with each other. As a consequence, the temperature of a mold wall is increased at a site corresponding to the cracked portion of the shell. In a surrounding area adjacent to the cracked portion of the shell, the temperature is increased through heat transmission from the cracked portion after a certain delay from occurrence of the cracked portion. Taking the above into consideration, a conventional breakout prediction system carries out prediction of the breakout by the use of a number of temperature sensors located on the mold wall for monitoring a temperature variation pattern of the mold wall to detect presence of the cracked portion in the shell.
A first example of such a conventional breakout prediction system is disclosed in a technical report entitled "Prediction System for Predicting Breakout in Continuous Casting by Neural Network Technique" contributed to Seitetsu Kenkyuu (=Iron Works Study), Vol. 399, pp. 31-34, 1990. A second example is disclosed in a book entitled "Applied Neural Network Techniques in Illustrative Cases" published by Triceps Corporation on Apr. 24, 1992, pp. 13-24.
In the first example, however, consideration is insufficient to the temperature variation pattern observed in the surrounding area adjacent to the cracked portion of the shell after the certain delay from occurrence of the cracked portion. Therefore, restriction is imposed on an improvement of precision in breakout prediction. In the second example, the prediction system has a complicated structure although the above-mentioned disadvantage in the first example is taken into consideration.